Mbonye Anthony K, Birungi Josephine, Yanow Stephanie K, Shokoples Sandra, Malamba Samuel, Alifrangis Michael, Magnussen Pascal
Ministry of Health, Kampala, Uganda, and School of Public Health, College of Health Sciences, Makerere University, Kampala, Uganda
Division of Entomology, Uganda Virus Research Institute, Entebbe, Uganda.
Antimicrob Agents Chemother. 2015 Sep;59(9):5475-82. doi: 10.1128/AAC.00507-15. Epub 2015 Jun 29.
The aim of this study was to assess the prevalence of mutations in Plasmodium falciparum dihydrofolate reductase (Pfdhfr) and dihydropteroate synthase (Pfdhps) genes among pregnant women using sulfadoxine-pyrimethamine (SP) as an intermittent preventive treatment (IPTp). A molecular epidemiological study of P. falciparum parasite resistance markers to SP was conducted from August 2010 to February 2012 in Mukono district in central Uganda. DNA was extracted from 413 P. falciparum-positive samples. Real-time PCR, followed by melting curve analysis, was used to characterize point mutations in the Pfdhfr and Pfdhps genes that are associated with SP resistance. The prevalence of the single-nucleotide mutations in Pfdhfr at codons 51I, 59R, and 108N and in Pfdhps at codons 437G and 540E was high (>98%), reaching 100% fixation after one dose of SP, while the prevalence of 581G was 3.3% at baseline, reaching 12.5% after one dose of SP. At baseline, the prevalence of Pfdhfr and Pfdhps quintuple mutations was 89%, whereas the sextuple mutations (including 581G) were not prevalent (3.9%), reaching 16.7% after one dose of SP. However, the numbers of infections at follow-up visits were small, and hence there was insufficient statistical power to test whether there was a true rise in the prevalence of this allele. The overall high frequency of Pfdhfr and Pfdhps quintuple mutations throughout pregnancy excluded further analyses of possible associations between certain haplotypes and the risk of lower birth weight and anemia. However, women infected with P. falciparum had 1.3-g/dl-lower hemoglobin levels (P = 0.001) and delivered babies with a 400-g-lower birth weight (P = 0.001) compared to nonparasitemic women. Despite this, 44 women who were P. falciparum positive at baseline became negative after one or two doses of SP (i.e., 50.5%), implying that SP-IPTp still has some efficacy. P. falciparum resistance markers to SP are high in this population, whereas P. falciparum infection was associated with poor birth outcomes.
本研究旨在评估使用周效磺胺-乙胺嘧啶（SP）作为间歇性预防治疗（IPTp）的孕妇中恶性疟原虫二氢叶酸还原酶（Pfdhfr）和二氢蝶酸合酶（Pfdhps）基因突变的流行情况。2010年8月至2012年2月在乌干达中部的穆科诺区开展了一项关于恶性疟原虫对SP耐药标志物的分子流行病学研究。从413份恶性疟原虫阳性样本中提取DNA。采用实时荧光定量PCR，随后进行熔解曲线分析，以鉴定与SP耐药相关的Pfdhfr和Pfdhps基因中的点突变。Pfdhfr基因51I、59R和108N密码子以及Pfdhps基因437G和540E密码子的单核苷酸突变流行率很高（>98%），一剂SP后达到100%固定，而581G密码子的流行率在基线时为3.3%，一剂SP后达到12.5%。基线时，Pfdhfr和Pfdhps五重突变的流行率为89%，而六重突变（包括581G）不常见（3.9%），一剂SP后达到16.7%。然而，随访时的感染例数较少，因此没有足够的统计效力来检验该等位基因的流行率是否真的上升。整个孕期Pfdhfr和Pfdhps五重突变的总体高频率使得无法进一步分析某些单倍型与低出生体重和贫血风险之间可能存在的关联。然而，与未感染疟原虫的女性相比，感染恶性疟原虫的女性血红蛋白水平低1.3 g/dl（P = 0.001），所生婴儿出生体重低400 g（P = 0.001）。尽管如此，44名基线时恶性疟原虫阳性的女性在一剂或两剂SP后转为阴性（即50.5%），这意味着SP-IPTp仍有一定疗效。该人群中恶性疟原虫对SP的耐药标志物水平很高，而恶性疟原虫感染与不良出生结局相关。
